📝 STANDARD DESCRIPTION:
High-Yield Points:
• Continuation of thoracic aorta after passing through aortic hiatus of diaphragm; lies on dorsal abdominal wall, slightly LEFT of midline.
• Visceral (unpaired) branches:
– Celiac a. — to stomach, liver, spleen, pancreas (foregut).
– Cranial mesenteric a. — to most of intestines (midgut).
– Caudal mesenteric a. — to descending colon and rectum (hindgut).
• Visceral (paired) branches: Renal aa., Testicular/Ovarian aa.
• Parietal (paired): Lumbar aa., Phrenicoabdominal aa.
• Terminal region: gives rise to paired external and internal iliac arteries and continues as the median sacral artery; branching order is species-specific.
📚 DETAILED DESCRIPTION:
ABDOMINAL AORTA — THE GREAT VISCERAL HIGHWAY
The aorta enters the abdomen via the aortic hiatus between the crura of the diaphragm. It runs caudally on the ventral surface of the lumbar vertebrae, slightly left of midline (the caudal vena cava lies to its right). Near the lumbosacral region it gives off the paired external and internal iliac arteries and continues caudally as the median sacral artery; the exact order and level vary by species.
UNPAIRED VISCERAL BRANCHES (foregut → hindgut):
1. Celiac Artery (T13-L1): The 'foregut artery'. Trifurcates into:
• Hepatic a. → liver and gall bladder.
• Left gastric a. → cardia of abomasum / stomach.
• Splenic a. → spleen, also ruminal branches.
2. Cranial Mesenteric Artery (L1-L2): The 'midgut artery'. Largest branch by territory. Supplies entire small intestine, cecum, ascending and transverse colon. Branches:
• Jejunal aa. (15-18 in number) → arcades supplying jejunum.
• Ileocolic, cecal, colic branches.
• Common site of verminous arteritis (Strongylus vulgaris) in horses → thrombosis → equine colic.
3. Caudal Mesenteric Artery (L4): The 'hindgut artery'. Small. Supplies descending colon and cranial rectum.
PAIRED VISCERAL BRANCHES:
• Renal aa. (right + left): paired, large; right longer (left kidney lies more caudally in ox). Most common origin for accessory renal aa.
• Testicular / Ovarian aa.: arise from ventral aorta; testicular artery descends to the scrotum and becomes highly convoluted; the surrounding testicular veins form the pampiniform plexus.
PAIRED PARIETAL BRANCHES:
• Phrenicoabdominal a. — to diaphragm + adrenal + caudal abdominal wall.
• Lumbar aa. — 6 pairs, between transverse processes; supply lumbar muscles and spine.
CAUDAL BRANCHES NEAR THE LUMBOSACRAL REGION (species-specific order):
• External iliac a. → main artery of hindlimb.
• Internal iliac a. → pelvic viscera.
• Median sacral a. → continues caudally as the median caudal artery (palpated for pulse on tail in cattle).
// COMPARATIVE ANALYSIS
| OX |
Aorta ends by giving off external iliacs, then continues as median sacral. Coccygeal pulse used clinically. |
| HORSE |
Cranial mesenteric a. is a major site of verminous arteritis from Strongylus vulgaris larvae — thromboembolic colic. |
| DOG |
Femoral artery (continuation of external iliac) used to record pulse in dog. Aortic thromboembolism ('saddle thrombus') causes acute hindlimb paralysis in cats. |
CLINICAL RELEVANCE
Aortic Thromboembolism (Cat): 'Saddle thrombus' lodges at terminal aorta → acute paralysis with cold hindlimbs ('blue feet'). Verminous Arteritis (Horse): Strongylus vulgaris larvae in cranial mesenteric a. → thrombi → intestinal infarction → colic. Renal artery stenosis rare in animals.
